1. Field of the Invention
The present invention relates to optical devices that enable a viewer to observe objects at night or during other low-light conditions. More specifically, the present invention relates to a handheld night vision monocular device with a unistructural optical bed that increases quality and enables the monocular to be manufactured with both reduced labor and cost.
2. Description of the Prior Art
Night vision devices are widely used in the military to provide soldiers, aviators and sailors with the ability to view objects at night or during other low light conditions. As a result, many night vision devices are currently being manufactured according to exacting military specifications and designs. Similarly, many such night vision devices are being manufactured for specific military applications such as part of the sights of various weapons or as part of goggle assemblies that attach to an aviator's or soldier's helmet. As a consequence, many of the night vision devices currently being manufactured are neither affordable nor easily adapted to non-military uses by the general public.
Night vision devices typically include an image intensifier tube that converts low intensity and/or infrared energy into visible light. Such night vision devices typically require sophisticated power supplies and circuitry to control the operation of the image intensifier tube and sophisticated optical arrangements that direct the infrared energy into the intensifier tube and visible light away from the image intensifier tube. In military applications, the various military personnel are trained in how to use and adjust the night vision devices they are issued. However, a night vision device designed for use by the general public must have simple adjustments that can be readily operated by a variety of different users in a dark environment. Preferably, a night vision device designed for the general public would have little or no adjustments so that a person need only turn on the device and look through it to obtain night vision.
As military sales wain, more and more night vision devices are being marketed directly to the general public. However, few of such prior art night vision devices are designed to be both low cost and east to operate. ITT Corporation, the assignee herein, manufactures a variety of night vision devices for military and the general public. Examples of some of the handheld night vision devices that are being sold to the public are shown in U.S. patent application Ser. No. 08/108,989 entitled NIGHT VISION BINOCULARS, filed Aug. 18, 1993 and U.S. patent application Ser. No. 08/405,172 entitled COMPACT NIGHT VISION DEVICE, filed Mar. 16, 1995. Such prior art night vision devices are far easier to use and are much less expensive than are their military counterparts. However, even these night vision devices have complex focusing mechanisms and folded optics that add significantly to the overall cost of the night vision device.
Some of the most expensive components contained within a night vision device are the various lenses used in the optical train of the night vision device. Not only are the optical elements themselves expensive but the assembly of the optics into an optical train is typically highly labor intensive. Lens elements must be exactly spaced in order to perform properly. This means that a night vision housing must be manufactured to exacting tolerances if the housing is used to retain the various lens elements in place. Molding plastic housings to exacting tolerances require highly complex molding tools and expensive raw materials. The molding of plastic housings to exacting tolerances also results in a high percentage of scrap parts that do not meet the required specifications. Even if proper housings are provided, a great deal of labor is still required in order to mount the various lens elements into the housing. The labor intensive procedure adds greatly to the overall cost of the night vision device and produces a device whose quality depends upon the skill by which that device was assembled.
In the prior art, many night vision devices have been designed with simplified optics in order to reduce the cost of the night vision device for the commercial marketplace. Such night vision devices are exemplified by co-pending U.S. patent application Ser. No. 08/497,200 to Palmer, the inventor herein, entitled NIGHT VISION MONOCULAR WITH BALANCED OPTICS and assigned to ITT Corp., the assignee herein. Although such other night vision devices do have low cost optics, the optics are still held in place and are aligned by the shape of the night vision housing. Consequently, the quality of the night vision device is highly dependent upon how exactly the housing of the night vision device is manufactured and how well the various optical components are assembled within the housing of the night vision device.
It is therefore an objective of the present invention to provide a night vision device with a simple, low-cost optical bed that is not part of the night vision device housing and is capable of retaining the various optical elements along the optical path in an exacting manner
It is a further object of the present invention to provide a method of assembling a night vision device using a low-cost optical bed.